Kubernetes Pod回收過程中如何處理gRPC流斷開？

如何實現gRPC 用戶端重新連接的彈性

在Kubernetes 叢集內建立gRPC 客戶端彈性重要處理Pod 回收場景的措施。透過利用 clientconn.go 的功能，您可以自動化 RPC 連接的重新連接流程。但是，管理流程需要手動幹預。

辨識流斷開問題

在 pod 回收的情況下，clientconn.go 會自動重新連接 RPC 連線。但是，流仍處於斷開狀態，需要建立新流。

解決方案：具有重試機制的流管理

要解決此問題，請實現以下偽-等待RPC連接進入READY狀狀態並建立新的程式碼Stream:

func (grpcclient *gRPCClient) ProcessRequests() error {
    defer grpcclient.Close()    
    
    go grpcclient.process()
    for {
      select {
        case <- grpcclient.reconnect:
           if !grpcclient.waitUntilReady() {
             return errors.New(&quot;failed to establish a connection within the defined timeout&quot;)
           }
           go grpcclient.process()
        case <- grpcclient.done:
          return nil
      }
    }
}

func (grpcclient *gRPCClient) process() {
    reqclient := GetStream() //always get a new stream
    for {
        request, err := reqclient.stream.Recv()
        log.Info(&quot;Request received&quot;)
        if err == io.EOF {          
            grpcclient.done <- true
            return
        }
        if err != nil {
            grpcclient.reconnect <- true
            return
            
        } else {
            //the happy path
            //code block to process any requests that are received
        }
    }
}

func (grpcclient *gRPCClient) waitUntilReady() bool {
  ctx, cancel := context.WithTimeout(context.Background(), 60*time.Second) //define how long you want to wait for connection to be restored before giving up
  defer cancel()
  return grpcclient.conn.WaitForStateChange(ctx, conectivity.Ready)
}

替代重新連接策略

更準確的方法是追蹤目前連線狀態並使用Connect 函數手動重新連線：

func (grpcclient *gRPCClient) ProcessRequests() error {
        defer grpcclient.Close()    
        
        go grpcclient.process()
        for {
          select {
            case <- grpcclient.reconnect:
               if !grpcclient.isReconnected(1*time.Second, 60*time.Second) {
                 return errors.New(&quot;failed to establish a connection within the defined timeout&quot;)
               }
               go grpcclient.process()
            case <- grpcclient.done:
              return nil
          }
        }
}

func (grpcclient *gRPCClient) isReconnected(check, timeout time.Duration) bool {
  ctx, cancel := context.context.WithTimeout(context.Background(), timeout)
  defer cancel()
  ticker := time.NewTicker(check)

  for{
    select {
      case <- ticker.C:
        grpcclient.conn.Connect()
 
        if grpcclient.conn.GetState() == connectivity.Ready {
          return true
        }
      case <- ctx.Done():
         return false
    }
  }
}

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